Building novel binding ligands to B7.1 and B7.2 based on human antibody single variable light chain domains.

Ligands specific for B7.1 (CD80) and B7.2 (CD86) have applications in disease indications that require inhibition of T-cell activity. As we observed significant sequence and structural similarity between the B7-binding ligand, cytotoxic T-lymphocyte associated protein-4 (CTLA-4), and antibody variable light chain domains (VLs), we have explored the possibilities of making novel B7 binding molecules based on single VL domains. We first describe the "rational" design and construction of a VL/CTLA-4 hybrid molecule in which we have grafted both the CDR1 and CDR3-like loops of CTLA-4 onto a single VL light chain, at sites determined by sequence and structure-based alignment. This molecule was secreted as a soluble product from Escherichia coli, but did not show any binding to B7.1 and B7.2. In a second approach we constructed a VL library in which human VL genes derived from B-cells were spiked with the CDR3-like loop of CTLA-4 and further diversified by DNA shuffling. This library was displayed on phage, and after selection gave B7.1 binding ligands which competed with CTLA-4. In order to evaluate the possible general utility of VL domains as binding ligands, we have constructed a non-biased VL library. From this DNA-shuffled human VL library we have selected single VL domains specific for B7.1, B7.2 or human IgG. Two B7.1-specific VL ligands and one B7.2-specific VL ligand showed competition with CTLA-4. One candidate VL domain-specific for B7.1 was affinity matured by simultaneous randomisation of all CDR loops using DNA shuffling with degenerate CDR-spiking oligonucleotides. From this library, a single VL domain with affinity of 191 nM for B7.1 was obtained, which also showed binding to B7.1 in situ. This VL had mutations in CDR1 and CDR3, indicating that antigen recognition for this single VL is most likely mediated by the same regions as in the VL domain of whole antibodies. The B7.1 and B7.2-specific VL domains described in this study may form the basis of a new family of immunomodulatory recombinant molecules. Furthermore, our studies suggest that it is feasible to create specific single VL domains to diverse targets as is the case for single VH domains.

van den Beucken T ，van Neer N ，Sablon E ，Desmet J ，Celis L ，Hoogenboom HR ，Hufton SE ... -  《JOURNAL OF MOLECULAR BIOLOGY》

A novel bispecific tetravalent antibody fusion protein to target costimulatory activity for T-cell activation to tumor cells overexpressing ErbB2/HER2.

Biburger M ，Weth R ，Wels WS 《JOURNAL OF MOLECULAR BIOLOGY》

The critical role of arginine residues in the binding of human monoclonal antibodies to cardiolipin.

Giles I ，Lambrianides N ，Latchman D ，Chen P ，Chukwuocha R ，Isenberg D ，Rahman A ... -  《-》

Design and expression of soluble CTLA-4 variable domain as a scaffold for the display of functional polypeptides.

We have designed and engineered the human cytotoxic T-lymphocyte associated protein-4 (CTLA-4) variable (V-like) domain to produce a human-based protein scaffold for peptide display. First, to test whether the CTLA-4 CDR-like loops were permissive to loop replacement/insertion we substituted either the CDR1 or CDR3 loop with somatostatin, a 14-residue intra-disulfide-linked neuropeptide. Upon expression as periplasmic-targeted proteins in Escherichia coli, molecules with superior solubility characteristics to the wild-type V-domain were produced. These mutations in CTLA-4 ablated binding to its natural ligands CD80 and CD86, whereas binding to a conformation-dependent anti-CTLA-4 monoclonal antibody showed that the V-domain framework remained correctly folded. Secondly, to develop a system for library selection, we displayed both wild-type and mutated CTLA-4 proteins on the surface of fd-bacteriophage as fusions with the geneIII protein. CTLA-4 displayed on phage bound specifically to immobilized CD80-Ig and CD86-Ig and in one-step panning enriched 5,000 to 2,600-fold respectively over wild-type phage. Bacteriophage displaying CTLA-4 with somatostatin in CDR3 (CTLA-4R-Som3) specifically bound somatostatin receptors on transfected CHO-K1 cells pre-incubated with 1 microg/ml tunicamycin to remove receptor glycosylation. Binding was specific, as 1 microM somatostatin successfully competed with CTLA-4R-Som3. CTLA-4R-Som3 also activated as well as binding preferentially to non-glycosylated receptor subtype Sst4. The ability to substitute CDR-like loops within CTLA-4 will enable design and construction of more complex libraries of single V-like domain binding molecules. Proteins 1999;36:217-227.

Nuttall SD ，Rousch MJ ，Irving RA ，Hufton SE ，Hoogenboom HR ，Hudson PJ ... -  《-》

Improvement of anti-Burkholderia mouse monoclonal antibody from various phage-displayed single-chain antibody libraries.

To improve anti-Burkholderia monoclonal antibody (MAb) binding affinity, six single chain variable fragments (scFvs) constructed previously were used as scaffolds to construct large highly-diversified phage-displayed mouse scFv random and domain libraries. First, we employed random mutagenesis to introduce random point mutations into entire variable regions, generating six random libraries. Additionally, the oligonucleotide-directed mutagenesis was targeted on complementarity-determining region 3 (CDR3) from each variable region of heavy (VH) and light chains (VL) derived from six scFvs, and generated eighteen domain libraries including six VH CDR3, six VL CDR3, and six combined VH/VL CDR3 mutated domains, respectively. We collected high scFvs binders through panning experiment over the large (size ~1 × 10⁹) random and domain libraries. The quality of the libraries was validated by successful selection of high-affinity clones. Random mutagenesis generated many mutant scFv clones having more than one amino acid changes around framework regions, but not many in CDRs. Surprisingly, the resulting eight higher scFv binders were selected from CDR3 mutations, but not from random mutations. Six of them resulted from CDR3 mutations of light chain, except for two scFvs from heavy chain, showing both Burkholderia pseudomallei and Burkholderia mallei had preferentially influenced the VL CDR3. Furthermore, all eight higher scFvs converted to full format human IgG1 antibodies were expressed transiently in 293T cell line. Five chimeric MAbs showed improved higher binding activity, as much as 0.2-0.3 at O.D. 405 nm, than positive control MAbs. These libraries could be valuable sources for selection of anti-Burkholderia antibodies and discovery of the relevant epitope(s) for developing effective vaccines or therapeutics.

Kim HS ，Lo SC ，Wear DJ ，Stojadinovic A ，Weina PJ ，Izadjoo MJ ... -  《-》